微波加热制备SiC/Mullite球体的工艺和性能

Synthesis and Characterization of SiC/Mullite Spheres by Microwave Heating

以粉煤灰微珠和炭黑为原料,通过微波加热碳热还原法原位合成了SiC/Mullite球体。利用X射线衍射(XRD),场发射扫描电子显微镜(FESEM)对产物进行了物相和结构表征。研究表明:在1100～1300℃之间,微珠表面的SiO2通过固(SiO2)-固(C)反应机理而形成SiC,而内部Mullite依然维持微珠球形骨架,从而形成SiC/Mullite球体。温度高于1300℃时,SiC通过固-液-气机理定向生长为晶须且Mullite亦参与反应,从而使粉煤灰微珠失去其球形形貌。本试验的最佳工艺条件为n(C):n(SiO2)=4.2,温度1200℃下恒温1h。

Fly ash microspheres and carbon black were taken as raw materials to prepare SiC/Mullite microspheres by microwave heating carbon thermal reduction.X-ray diffraction（XRD） and field emission scanning electron microscopy（FESEM） were applied to characterize the phase composition and microstructure of SiC/Mullite spheres.The phase composition and the structure were characterized by XRD and FESEM.The results show that the reaction mechanism mainly associates with solid-solid reaction between C（s） and SiO2（s） on the surface of fly ash microspheres with its spherical shape unchanging when the temperature is between 1100-1300 oC.When the temperature is higher than 1300 oC,SiC has easier orientation growth into whisker through VLS mechanism for the presence of liquid phase.Mullite is involved in the reaction;therefore,fly ash microspheres cannot maintain its spherical shape.The optimum conditions of our experiments are n（C）：n（SiO2）=4.2,1200 oC and 1 h.